Seabird interactions with longlining operations for Dissostichus eleginoides around South Georgia, April to May 1994
Longlining operations for Dissostichus eleginoides off South Georgia were assessed for incidental mortality and interactions with seabirds. Twenty-seven line sets were observed and 98 deaths of seabirds were recorded over 20 sets; no deaths occurred during hauls. The 16 sets made at night contributed 15% of overall mortality, all of white-chinned petrels (Procellaria aequinoctialis); the four day sets contributed 85% of deaths, with giant petrels (Macronectes sp.), grey-headed albatrosses (Diomedea chrysostoma) and black-browed albatrosses (D. melanophrys) predominating. Grey-headed albatrosses, whose populations (at South Georgia are in serious decline, were disproportionately affected in relation to their numbers near the fishing vessel; giant petrels may be disproportionately affected in relation to the size of their breeding population at South Georgia when compared to albatrosses. The average mortality rate for the 20 sets was 0.48 birds/1 000 hooks and maximum mortality 3.12 birds/1 000 hooks. Mortality and interactions of birds with operations varied with site and time of day, and was affected by behavioural interactions between birds. Setting only at night would dramatically reduce the number of albatross deaths, and restrict mortality to white-chinned petrels. A streamer line made to CCAMLR specifications may reduce mortality but may be less effective during calm weather, intense feeding activity by seabirds, or when incorrectly constructed.